from tkinter import *

master = Tk()

frame = Frame(master)
frame.pack(padx = 10, pady = 10)

v1 = StringVar()
v2 = StringVar()
v3 = StringVar()
def test(content):
    return content.isdigit()

testCMD = master.register(test)
e1 = Entry(frame, width = 10, textvariable = v1, validate = 'key', validatecommand = (testCMD, '%P')).grid(row = 0, column = 0)

Label(frame, text = '+').grid(row = 0, column = 1)

e2 = Entry(frame, width = 10, textvariable = v2, validate = 'key', validatecommand = (testCMD, '%P')).grid(row = 0, column = 2)

Label(frame, text = '=').grid(row = 0, column = 3)

e3 = Entry(frame, width = 10, textvariable = v2, validate = 'key', validatecommand = (testCMD, '%P')).grid(row = 0, column = 4)

def calc():
    result = int(v1.get()) + int(v2.get())
    v3.get(str(result))

Button(frame, text = '计算结果', command = calc).grid(row = 1, column = 2, pady = 5)

mainloop()
